A New Recognition Method for Damping Coefficients of Rod Pumping System of Directional Well

摘要

In this paper, a pattern recognition method is put forward to identify damping coefficients of rod pumping system of directional well by using characteristics space mapping. The 24-direction chain code is presented to encode the curve of dynamometer card. The parametric equation of the dynamometer card curve is transformed into Fourier series whose coefficients can be computed according to the curve's chain codes. By means of those Fourier coefficients, shape characteristics of the curve are extracted. Euclidean distance is introduced as the measurement of similar degree between the shape characteristics of measured dynamometer card and that of simulated dynamometer card. Changing the value of viscous damping coefficient and Coulomb damping coefficient in the simulation program, different simulated dynamometer cards are obtained. Substituting their shape characteristics to the Euclidean distance, respectively, a series of distances are acquired. When the distance is little than the given error, the corresponding values of the damping coefficients in the simulation program are regarded as real damping coefficients of the rod pumping system of directional well. In the end, an example is provided to show the correctness and effectiveness of the presented method.